Beck, who owns and runs The Blaze, made the announcement in Iowa, at a rally hosted by a pro-Cruz super PAC, and is slated to appear with Cruz again Saturday evening at a second rally.

"We need a new George Washington. Today's Washington will not be found in the garish light of gold but rather in the bold service of a man who stands tirelessly for what he deeply believes. That government should be of the people, by the people, and for the people. That is why I'm endorsing Sen. Ted Cruz as the next President of the United States of America," Beck said in a statement released as he spoke, noting that he had not previously endorsed a candidate in 40 years of broadcasting.

The endorsement gives Cruz a boost in Iowa following a rough week, in which former GOP vice presidential nominee Sarah Palin, who maintains some cache with the conservative grassroots, endorsed Donald Trump.

Another blow came when Iowa Gov. Terry Branstad said last week that he does not want Cruz to win Iowa because of his opposition to the ethanol mandate. Most polls show that Cruz and Trump are locked in a close fight for first place, though a CNN/ORC poll out Thursday found Cruz trailing Trump by a wider margin. The two have been trading increasingly sharp criticisms, including via new advertisements.

On Saturday, Beck made clear that he stands squarely in Cruz's camp.

"If Donald Trump wins, it's going to be a snowball to hell," he said at the rally, at other points noting Trump's past record of donating to Democrats and characterizing Trump as a bully.

Cruz appeared onstage with him after the announcement and went on to warn attendees about politicians who promise one thing on the campaign trail and do another in Washington -- and to urge that voters not get "burned again," a case he has been making increasingly frequently since the last GOP presidential debate, when he began highlighting liberal positions Trump once espoused.

Cruz's backers have been touting the coming Beck endorsement as the Cruz-Trump battle intensifies.

Rep. Steve King (R-Iowa), an influential conservative congressman who is one of Cruz’s national co-chairs, told POLITICO earlier this week: “To quote Donald Trump, that’s huge. I’ll match Palin with [“Duck Dynasty” star] Phil Robertson, and then raise you a Glenn Beck.”

Beck, who has supported Cruz for years, is far from the only conservative media personality to call Cruz his favorite. As Trump has increased his attacks on Cruz in the past few weeks, talk radio has rallied around the Texas Senator, showing he has strong support among an important group of influencers with millions of listeners.

Trump, who has long been bashing Beck, took another swipe at the radio host on Saturday via Twitter.

"Failing @GlennBeck lost all credibility. Not only was he fired @ FOX, he would have voted for Clinton over McCain" Trump wrote.

Beck responded in kind.

"It's amazing how much time this presidential candidate is spending on someone who is so "irrelevant" cc @realDonaldTrump" Beck tweeted.